Odorant binding proteins (OBP) are the most abundant components of the lymph in the antenna of insects.
These proteins are believed to participate in transport, protection and/or inactivation of information in the early events of insect olfaction.
Odorant binding proteins have been studied in Lepidoptera, where these are divided into two groups at least.
The pheromone binding proteins (PBP) belong to one group of the odorant binding proteins and have been distinguished as proteins which participate in recognition of (sex) pheromones.
Further, the proteins which belong to another group of the odorant binding proteins participate in the recognition of general odorants (general odorant binding proteins, GOBP).
The pheromone binding proteins which participate in recognition of sex pheromones have been detected and characterized in a number of species from several insects orders since the first identification of these proteins in Antheraea pilophemus.
Functionally, these proteins can be classified as lipocalins, a group of proteins binding hydrophobic ligands.
However, insect odor molecular binding proteins (insect OBP) share little homology with other lipocalins, which are primarily composed of 8 or 10 antiparallel .beta.-strands forming .beta.-barrel.
Circular dichroism measurement and theoretical structure calculation revealed that insect OBPs are in a large part .alpha.-helical.
Therefore, the study of 3-dimensional structure and that of ligand binding of insect OBPs enable to get a better understanding of the role of these proteins in the olfactory Processing.
Though reasonable Amount of functional OBP has been desired for the research in various fields, the isolation of sufficient amount of nature?? protein is out of the question.
Insect odor molecular binding proteins have been previously expressed both in bacterial and eukaryotic systems.
Antheraea pernyi has been expressed in the baculovirus system, but it's not a perfect method for the production of sufficient amount of insect OBP because of low yield.
While the PBP from Antheraea polyphemus has been expressed in low yield in Escherichia coli, the product is physiologically inactivated and required refolding for structural and functional studies.
Therefore, a method which enable to provide sufficient amount of insect OBP, furthermore, to overexpress under the condition of physiological activation has been in demand.